Privacy communications method and means employing frequency shifting of components of voice signals



Dec. 9. 1.969 A. w. BARBER 3,483,326

PRIVACY COMMUNICATIONS METHOD AND MEANS EMPLOYING FREQUENCY SHIFTING OF COMPONENTS OF VOICE SIGNALS Filed Oct. 16, 1967 RECORDING PLAY BACK ELECTRONICS ELECTRONICS T 39 TWO WAY CODING 62 AND DECODING O INVENTOR.

BY e/m/ w- Barber- United States Patent 3,483,326 PRIVACY COMMUNICATIONS METHOD AND MEANS EMPLOYING FREQUENCY SHIFT- ING OF COMPONENTS OF VOICE SIGNALS Alfred W. Barber, Bayside, N.Y. (3244 Francis Lewis Blvd., Flushing, N.Y. 11358) Continuation-impart of application Ser. No. 655,708, June 22, 1967. This application Oct. 16, 1967, Ser. No. 675,579

Int. Cl. H04m 1/70, 3/16 US. Cl. 179-1.5 6 Claims ABSTRACT OF THE DISCLOSURE The present application is a continuation-in-part of the application entitled Privacy Communications Device Using Key Controlled Frequency Changing of Audio Signals and Magnetic Recording or the Like filed June 22, 1967 and bearing Ser. No. 655,708.

BACKGROUND OF THE INVENTION Field of the invention The present invention pertains to telephony class 179 and secret, sub-class 1.5.

Description of the prior art There are many ways to achieve privacy in voice communication. Basically these systems provide some means for rendering voice signals unintelligible, transmitting the unintelligible signals to a remote point and decoding the received signals to reproduce the original intelligence.

In accordance with the present invention voice communications in privacy are accomplished by raising and lowering component frequencies in accordance with a predetermined key. After transmittal to a remote point by wire or radio, the signals are restored to intelligible form by passing them through a distorting device with a key identical to the key at the transmitting point. The basic invention has been shown and described in a patent application entitled Privacy Communications Device Using Key Controlled Frequency Changing of Audio Signals and Magnetic Recording or the Like" which was filed June 22, 1967 and was given Ser. No. 655,708. The present improvement includes electronic operation by means of operational amplifiers, compounding the system and certain other modifications including an antibugging system.

Accordingly, one purpose of the present invention is to provide improvements in my basic system described in the application referred to above.

Another object is to provide greatly increased degrees of security by cascading two or more of my key controlled secrecy communications devices.

A further object is to provide an improvement particularly aimed at bugging situations.

3,483,326 Patented Dec. 9, 1969 Ice A still further object is to provide operational amplifier feedback control for electronic control of my secrecy system.

These and other objects will be apparent from the detailed description of the invention given in connection with the various figures of the drawing.

BRIEF DESCRIPTION OF THE DRAWING FIGURE 1 is a diagram partly in block form of a secrecy communication system in accordance with my present invention using operational amplifier and electrical feedback control means.

FIGURE 2 shows how my key controlled system can be cascaded to provide higher degrees of secrecy.

FIGURE 3 shows an anti-bugging form of my present invention.

FIGURE 4 shows a modified form of key.

FIGURE 1 shows a form of my secrecy communication system in which block 1 may be taken to represent the electronics of a magnetic recording unit including suitable amplifiers, erase oscillator, bias oscillator, input and output circuits. The inputs for example, may be from a microphone 2 connected to the input of recording unit 1, over leads 3 and 4 and a record player including turntable 5 and pickup 6 connected to the input over leads 7 and 8. The magnetic recording is to be accomplished on a suitable magnetic surface such as narrow drum 18. The erasing is carried out by erase head 9 connected to suitable erase circuits in unit 1 over leads 10 and 11. The recording is performed on drum 18 by a suitable recording head 12 connected to the recording circuits of unit 1 over leads 13 and 14. The encoded or frequency distorted recordings are picked off drum 18 by pick-up head 15 connected over leads 16 and 17 to an output amplifier 37 the output of which is fed to the desired utilization means (such as a telephone line or radio transmitter, not shown) over leads 38 and 39. Drum 18 is mounted on a shaft 19 coupled to a shaft 21 carrying a driving motor 22 and a tachometer generator 20. In order to drive motor 22 (and hence drum 18) in accordance with a complex controlled speed pattern an operational amplifier 23 is provided. This amplifier includes an inverting input 24, a common terminal 25 and an output terminal 26. It is preferred that this amplifier be a differential amplifier so that its output applied to motor 22 over leads- 27 and 28 can be controlled in either polarity in order to tightly control the speed of motor 22 and hence drum 18. The operational amplifier 23 supplies power to motor 22 in accordance with input current applied to input terminal 24 and feedback determined by the value, of variable resistor 29 connected between output terminal 26 and input terminal 24. The input current to terminal 24 is determined by the circuit starting at common terminal 25, passing through generator 20, voltage source 31 and controlled variable resistor 30. The value of resistor 30 is controlled by key 32 carried on shaft 33 of motor 34 which, in turn, receives power over leads 35 and 36 from a suitable source, not shown. The closed loop feedback circuit provided by generator 20 connected back into the input circuit of amplifier 23 provides tightly controlled speed of motor 22 (and drum 18) in accordance with the contour of cam 32. The changes in speed thus provided while drum 18 is moving from recording head 12 to pick-up head 15 provides the frequency distortion of the voice frequency signals from microphone 2 (and music frequencies from the turntable 5 used to enhance the unintelligibility of the distorted speech) in accordance with the contour of key cam 32. Thus speech frequency signals distorted in accordance with a key are provided and fed to output leads 38 and 39.

In order to restore intelligibility as at a remote point, a similar device is used provided with an identical key. At

the receiver, the received signals are fed to an amplifier 1 in lieu of signals from a microphone and the output, which can be applied to a loudspeaker or earphone, appearing across leads 38 and 39, will be voice frequency signals in intelligible form and facsimiles of the original voice signals applied to microphone 2 at the transmitter or input end of the system.

FIGURE 2 shows how an enchanced degree of secrecy can be achieved by multiplexing the encoding process. It will be understood that the same components are used as shown in FIGURE 1 and described above, only motor 22, generator 20, drum 18 and heads 9, 12 and 15 being shown. Here, in FIGURE 2 motor 22 is provided with a shaft 40-44 carrying two encoding earns 41 and 45. These cams control variable resistors 43 and 47 respectively. These resistors are included in the circuits of the operational amplifier as, for example, one may be used in place of input resistor 30 and the other in place of feedback resistor 29. It will be understood that in order to provide ready changing o fthe encoding patterns that cams 41 and 45 as well as 32 (FIG. 1) should be readily removable so that a wide variety of different patterns may be quickly and easily provided. It is of course necessary that both ends of the system i.e. the encoding and decoding stations must be provided with identical cams.

FIGURE 3 shows a method by which the present invention may be used as an anti-bugging device. The two way coding and decoding device 48 may be taken to represent a complete two way device in accordance with the present invention. It is designed to operate to and from a telephone hand-set 49-50 connected over input/output leads 51-52-53 and to a loudspeaker 54 over leads 55-56 and from a telephone line 59-61. In operation a person close talks over hand-set 49-50 producing encoded loud secret speech at loudspeaker 54 from which the encoded signals are picked up by microphone 57 of hand-set 57-58 and then out over telephone lines 60-61. Return encoded signals from a similar system return over lines 59-62 to two way coding and decoding unit 48 and are presented in intelligible form in ear piece 50. The loud encoded signals from loudspeaker 54 produce unintelligible sounds to overcome the low close talking at microphone 49 and thereby obviate any bugging attempts.

FIGURE 4 shows a modified encoding cam 63 having a plurality of shaft holes 64, 65, 66, 67 and 68. This cam provides different encoding patterns, 5 by using each of the five shaft holes with the cam facing one Way and 5 more by facing the cam in the opposite direction. Such a cam used in the multiple carn device of FIGURE 2 will by interchanging cams and repeating the alternation of holes and sides, provide 100 different encoding patterns. It will be readily seen that an exceedingly large number of different encoding patterns can be readily provided.

While only a few forms of the present invention have been shown and described, many modifications will be evident to those skilled in the art and within the spirit and scope of the invention as set forth, in particular, in the appended claims.

I claim:

1. In a secrecy communication device, the combination of:

a magnetizable surface;

recording and play-back heads mounted in spaced relationship for recording on and playing back from said surface;

a variable speed motor for moving said surface past said heads;

a generator coupled to said motor;

an operational amplifier including an inverting input and an output;

coupling means between said output and said motor for driving said motor;

coupling means between said generator and said input;

a source of current coupled to said input;

and key controlled means for partially determining the output of said amplifier;

whereby said surface is moved past said heads at a rate which is in accordance with key.

2. A secrecy communication device as set forth in claim 1, and including means for applying voice signals to said recording head and means for utilizing encoded voice signals picked up by said play-back head.

3. A secrecy communication device as set forth in claim 1, wherein said key is a cam having a complex contour.

4. A secrecy communication device as set forth in claim 1, wherein said key controlled means includes a key controlled variable resistor connected in series with said source of current.

5. A secrecy communication device as set forth in claim 1, wherein said key controlle'd means includes a key controlled feedback resistor connected between the input and output of said amplifier.

6. A secrecy communication device as set forth in claim 1, wherein said key controlled means includes two key cams for controlling a variable resistor connected in series with said source of current and a variable feedback resistor connected between said input and said output.

References Cited UNITED STATES PATENTS 2,730,569 1/1956 Street 179l.5 X

RODNEY D. BENNETT, 111., Primary Examiner DANIEL C. KAUFMAN, Assistant Examiner US. Cl. X.R. 

